"So, today's classes were lots of fun," Cynthia Day of San Jose blogged from the Mathematical Olympiad Summer Program at the University of Nebraska at Lincoln.

"First we had polynomials with Po-Ru, where I got to brush up on interpolation. Then we did awesomely awesome constructions problems with Ian. Finally, in the afternoon, Carlos showed us some really cool angle-chasing problems.

"In fact, one of them is now my new favorite math problem!"

But the most awesomely awesome equations are still to come when Cynthia, 15, and seven teammates represent the United States at the 2010 China Girls Math Olympiad next week in Shijiazhuang, about 170 miles northeast of Beijing.

Three of the eight competitors come from the South Bay: Cynthia, who will be a junior at Lynbrook High in San Jose; Lynnelle Ye, a graduate of Palo Alto High; and Shiyu "Jing Jing" Li, who graduated from Cupertino High. The girls leave today.

It's the second time around for all three, who have competed in China before and emerged with medals. Math and science boosters hope the girls will inspire others in one of the few fields in which girls still lag behind boys.

Even as females surpass their male counterparts in many academic areas, girls still make up only a tiny fraction in elite math competitions; as in most past years, this year's USA Mathematical Olympiad team is all male. Women make up about 30 percent of graduate students in math and statistics, a proportion that has remained steady for 10 years, said Hélène Barcelo, deputy director of the Berkeley-based Mathematical Sciences Research Institute, which sponsors the girls team.

"It's sad. There are such great careers for these young women," said Laura Haas, an IBM fellow and director of computer science at IBM Research-Almaden, one of the team's financial backers. She ticks off the opportunities, from banking to business to space science, opened by math degrees.

The dearth of girls in math contests isn't just an American phenomenon. China started the Girls Math Olympiad in 2002 to encourage girls to compete in math, according to Zuming Feng, who has coached the U.S. girls team since its first invitation to the contest in 2007.

Feng, a teacher at Phillips Exeter Academy in New Hampshire, heartily promotes high-level competition. While many girls are capable of solving difficult problems, "to be on this team, they need to feel, 'I just want to show people that I am this good' " he said. Some girls don't feel they need to go after those bragging rights, he said.

It's not the showcasing of skills, but the challenge of tackling head-spinning problems that the girls say they relish. In each of the two days of competition, contestants are given four problems to solve in four hours.

For those who wonder why the girls team is heavily Asian-American, Feng believes that it has to do mostly with families valuing and stressing math education from the time children are young.

Lynnelle, 18, whose math project placed fourth in the prestigious Intel Science Talent Search, studied math with her China-educated grandmother. Cynthia's parents pushed her to take math enrichment courses.

Jing Jing, 16, who last year won a gold medal at the girls olympiad, said she's loved math "since I could count." Her dad, a software programmer who has a doctorate in math, served as her math teacher and gave her college textbooks to study. As a high school freshman she passed out of BC Calculus, the course normally offered advanced seniors.

All three girls said they feel the pressure to live up to expectations -- their own and others'. "This time I guess I feel more pressured since I did well last time and would like to do well again," said Lynnelle, who received a gold medal in 2008.

Awards are given for surpassing certain thresholds, and not for beating out all the competition. Gold medals are awarded to the top 8.5 percent of contestants, Feng said.

Cynthia acknowledges that facing the contest is a little stressful because she doesn't want to let down the half-dozen groups that are funding the trip.

Although she knows she should be studying, she's also busy with an earth sciences internship at Stanford University, and studying physics so she can advance to the AP course in the fall at Lynbrook.

Lynnelle, who was president of Palo Alto High's math club, tries, often futilely, to talk up math contests to her friends. A lot of people will say something like, "What, take a math test? Why would I do that?' " she said.

She's drawn to that moment of discovery, "the feeling when I figure out something important about a problem, or even better solve it completely," she said, "when I see, Oh! Everything fits together, and it's really elegant and beautiful."